default_value_for.rb

# Copyright (c) 2008, 2009, 2010, 2011 Phusion
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
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# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# THE SOFTWARE.

module DefaultValueFor
	class NormalValueContainer
		def initialize(value)
			@value = value
		end

		def evaluate(instance)
			if @value.duplicable?
				return @value.dup
			else
				return @value
			end
		end
	end

	class BlockValueContainer
		def initialize(block)
			@block = block
		end

		def evaluate(instance)
			if @block.arity == 0
				return @block.call
			else
				return @block.call(instance)
			end
		end
	end

	module ClassMethods
		def default_value_for(attribute, value = nil, &block)
			if !method_defined?(:initialize_with_defaults)
				include(InstanceMethods)
				alias_method_chain :initialize, :defaults
				if respond_to?(:class_attribute)
					class_attribute :_default_attribute_values
				else
					class_inheritable_accessor :_default_attribute_values
				end
				extend(DelayedClassMethods)
				init_hash = true
			end
			if init_hash || !singleton_methods(false).to_s.include?("_default_attribute_values")
				self._default_attribute_values = ActiveSupport::OrderedHash.new
			end
			if block_given?
				container = BlockValueContainer.new(block)
			else
				container = NormalValueContainer.new(value)
			end
			_default_attribute_values[attribute.to_s] = container
		end

		def default_values(values)
			values.each_pair do |key, value|
				if value.kind_of? Proc
					default_value_for(key, &value)
				else
					default_value_for(key, value)
				end
			end
		end
	end

	module DelayedClassMethods
		def _all_default_attribute_values
			return _default_attribute_values unless superclass.respond_to?(:_default_attribute_values)
			superclass._all_default_attribute_values.merge(_default_attribute_values)
		end
	end

	module InstanceMethods
		def initialize_with_defaults(attrs = nil, *args, &block)
			initialize_without_defaults(attrs, *args, &block)
			if attrs
				stringified_attrs = attrs.stringify_keys
				safe_attrs = if respond_to? :sanitize_for_mass_assignment
					sanitize_for_mass_assignment(stringified_attrs)
				else
					remove_attributes_protected_from_mass_assignment(stringified_attrs)
				end
				safe_attribute_names = safe_attrs.keys.map do |x|
					x.to_s
				end
			end
			self.class._all_default_attribute_values.each do |attribute, container|
				if safe_attribute_names.nil? || !safe_attribute_names.any? { |attr_name| attr_name =~ /^#{attribute}($|\()/ }
					__send__("#{attribute}=", container.evaluate(self))
					changed_attributes.delete(attribute)
				end
			end
			yield(self) if block_given?
		end
	end
end

if defined?(Rails::Railtie)
	require 'default_value_for/railtie'
else
	# Rails 2 initialization
	ActiveRecord::Base.extend(DefaultValueFor::ClassMethods)
end